Wireless selection system



New: 27 1923 1,475297 R. B. GOLDSCHMIDT WIRELESS sELEcTIbu SYSTEM FiledJune 25. 1920 L Feceiver Patented Nov. 27, 1923.

ROBERT BENEDICT Gennscrmzrnzr, or PARIS, FRANCE.

wrnannss SELECTION SYSTEM.

Application filed .Tune 25, 1920. Serial No. 391,789.

(GRANTED UNDER THE PROVISIONS OE THE ACT OF MARCH 3, 1921, 41 STAT In.1313.)

To all whom it may concern:

Be it known that I, Bonner BENEDICT GoLnscHMIn'r, a subject of the Kingof Belgium, residing at 350 Rue Saint Honore, Paris, France, haveinvented certain new and useful Improvements in Wireless SelectionSystems (for which I have filed applications for patents in BelgiumDecember 29, 1913, and addition on May 2, 1914; Great Britain, June 12,1914, andaddition on June 23, 1914:; Germany, May 25, 1914:; and FranceJanuary 20. 1920), of which the following is specification.

Communication by electromagnetic waves is frequently disturbed at areceiving station either by extraneous signals or by atmosphericdischarges collected by the antenna together with the waves intended tobe received.

Electrical systems of selection, dependent on syntony, are very ofteninsufficient to eliminate extraneous signals, if powerful or much dampedor of a wave length approximating to that of the wave to be received,and are nearly ineffective against severe atmospheric disturbances.

The purpose of the apparatus forming the subject of the presentapplication is to effect a mechanical selection of the signals collectedby the receiving antenna in order to eliminate parasitic signals.

This mechanical selection is applicable to all receiving systems,whatever electrical method of selection. which is generally based onsyntony, be employed.

The principle of the system is as follows i There being a receiver and areceiving antenna, a commutator is inserted in the antenna circuit bywhich the antenna can be connected to or disconnected from the receiverwith afrequency equal to the frequency of the trains of waves it isdesired to receive, the time of opening and closing of the circuit beingmoreover regulable.

In other words, the receiving apparatus is only connected with theantenna during the time of reception of each train of waves of theradiation to be recorded,.and no other can influence it.

Supposing that the radiation to be received gives a musical note of afrequence of 500, that is to say there are 500 trains of waves persecond, the antenna will be connected to the receiver 500 times asecond, connection being made before the passage of each train of wavesand broken after it. It will be readily understood that extraneousradiations or atmospheric perturbations will only be able to operate'onthe receiver if the trains of waves of which they consist are collectedexactly at the instant when the antenna and receiver are joined; whichcan only happen by accident and cannot disturb the main radiation whichis tobe received.

The two principal conditions which should be realized in such a systemare (l) Synchronis'm between the interruptions of the receivingcommutator and the succession of trains of waves of the radiation to bereceived, that is to say f f (2) Agreement of phase between the closingof the circuit between antenna and receiver by the commutator and thepassage of each train of waves.

Synchronism can be secured by means of various mechanical, electrical,magnetic, electromagnetic or other regulators or commutators, which atthe transmitting station ensure the radiation of a regular and uniformsucession of trains of waves, and at the receiving station ensure theconnection of the receiver with the antenna during, and only during, thepassage of each train of waves, the regulator of the receiving stationbeing synchronized with that of the transmitting station.

Agreement of phase of the second and receiving apparatus is easilyobtained, at the receiving station, by regulating the relative positionof the fixed contact and of the axis of the commutator.

The frequency ofinterruption of the commutator may be equal to, or amultiple or sub-multiple of the frequency of the trains of waves, moreparticularly in the case of radiations'in which use is made ofalternating current to charge the condenser,

and of the attenuation of the spark'by resonance with thelow frequencycircuit.

station; whether 2000 (one spark per half wave of alternator E. M. E),or 1000 (one spark for each complete alternation), or 606 (one spark inthree half waves of E. M. F.) or 500, etc., according to the degree ofattenuation of the spark.

There may in some cases (for instance with a note of 2000 or of 666frequency) be a change in the musical note, which in the former casewill be converted into a note of 1000 frequency and in thesecond caseinto one of frequency 333.

The commutator may be placed elsewhere than in the antenna circuit, forinstance in the secondary circuit of the re-- ceiver, or in thetelephone circuit, or in any other circuit provided that it fulfils thecondition above set out, viz to remove the telephone or recordingapparatus from the influence of antenna between each two trains ofwaves.

If a receiving station commonly receives messages at two or threedifferent frequencies a similar number of commutators may be employedconnected in parallel and rotating at speeds corresponding to thesedifferent frequencies.

The commutator may be made in any desired fashion so long as it fulfilsthe conditions above set out concerning the regulation of the frequency,of the phase and of the time of interruption.

Take for instance a rotary commutator or a vibratory interrupter.

In the accompanying drawings, Fig. 1 shows diagrammatically theapplication of this system toa transmitting station; while Figs. 2 and 3show its application to the receiving station.

A is the transmitting antenna, joined to earth at T through the sparkgap-O supplied by the induction coil I.

The primary circuit of the coil, supplied by the source P is regularlyinterrupted by the aid of the toothed wheel B on which the contact Dbears. There is insulation between the teeth.

The wheel being rotated at a uniform speed, controlled by aspecialregulator, the frequency of the sparks, and in consequence, of thetrains of waves, will be equal to the product of the speed and thenumber of teeth, say f A key M allows Morse signals to be sent.

For a greater simplicity, the accessories, relays and so on adapted toensure good electrical and mechanical operation are not shown on thedrawings.

The apparatus for regulating the speed can be of any suitablekind,mechanical, clockwork, electrical, or the like. It can be rotary,vibratory, oscillatory, and can be combined either directly orindirectly with the wheel B. This wheel can equally be replaced by avibratory or oscillatory system.

The commutator B or similar apparatus can work in various ways, at thetransmitting station, to regulate the frequency of the trains of waves.Fig. 1 shows only one par ticular instance.

Itcan operate directly on generators, to produce an alternating current,of which it regulates the frequency, or again it can be employed as atikker at the bottom of the antenna, especially in the case whencontinuous waves are used.

Figures 2 and 3 relate to the receiving station. A indicates thereceiving antenna, R a receiver, T earth. The commutator wheel B,equivalent to the wheel B of the transmitting station can be connectedin this circuit.

This wheel rotates at a speed and carries a number of teeth or segmentssuch that the frequency of the interruptions is equal to 5 that of thetrains of waves, controlled by B at the transmitting station.

Further, the contact D is for the purpose of the present invention fixedon another wheel E concentric with B and insulated from it electrically.By moving this contact by an amount at most equal to the pitch of thewheel B it will always be possible to secure agreement of phase betweenthe wave trains and the successive contacts of D with the teeth of B cIt is obvious that the speed regulating apparatus of the wheel B can bemade similar to that at the sending station or of other appropriatetype.

Further, the commutator wheel B can be inserted in any other circuit ofthe receiving station besides the antenna circuit, for example either inthe secondary circuit 'or' in the telephone circuit, etc., provided thatit fulfils the condition stated above, viz to withdraw the telephone orreceiving apparatus from the influence of the antenna between two trainsof waves.

Now suppose absolute synchronism be 119 tween the trains of waves andthe interruptions of the commutator at the receiving station is notattained or has been destroyed, that is to say the case in which f z fl;where is the frequency of the commutator at the receiving station and f,the frequency of the trains of waves transmitted. This can be remediedat the receiving station by continuously regulating the relativeposition of the wheel E and the wheel B In other words, if a, is thenumber of segments or teeth of the wheel B and 2),, its angular speed, f:n v,.

If f z it will sufiice to impress upon the wheel hi an angular speedequal to revolutions per second.

This angular speed is determined experi- 130 mentally by leaving thewheel E stationary and noting the aeriodic time T of the interferencesbetween the trains of waves and the interruptions of the commutator B Wehave further T seconds.

Practically, the periodic time 'I of-the interferences is determinedvery easily; if the wheel E is stationary, the signals being receivedintermittently, it is suflicient to notice the time between twosuccessive reappearances of the signals.

/Vhen synchronism is perfect, the signals are received continuously ormore usually, the silence is permanent; in this latter case it is thensuflicient to regulate once for all the position of the contact D whichregulates the phase to obtain a continuous reception.

hen the difference 7,, f, is exceedingly small, the periodic time Tbecomes con siderable and the speed V to be impressed upon the wheel Every low.

It is then suflicient to correct from time to time the position of thecontact D by hand.

If the difference f,;, is appreciable, the

Whence rotation of the wheel E can be obtained mechanically and itsregulation to the speed V brought about by any effective means.

In order to avoid static charge on the receiving antenna between thepassage of two trains of waves, which would produce a parasiticoscillation on connection to the receiver, a second contact like D canbe provided, which puts the wheel B directly to earth between thesuccessive passages of the teeth of this wheel under the contact DHaving now particularly described and ascertained the nature of my saidinvention and in what manner the same is'to be performed, I declare thatwhat I claim is:

1. A wireless telegraphy system comprising a transmitting station with aregulator to ensure a regular and uniform succession of trains of wavesand a receiving station with a regulator to cause the receiver to comeinto operation only during the time of transmission of such trains.

2. A wireless telegraphy system comprising a transmitting station with aregulator 3. A wireless receiving station with a commutator arranged toput the antenna into and out of operative relation with the receiver ata frequency equal to a multiple of that of the trains of waves to bereceived, and means to regulate the speed of the commutator.

4:. A wireless receiving station comprising an antenna, a receiver, acommutator arranged to put the antenna and receiver into and out ofoperative relation with a frequency fixed with respect to that of thetrains of waves to be received, and means to ensure coincidence betweensuccessive connections of the receiver with the antenna and thebeginning of successive receiving trains of waves.

5. A wireless receiving station comprising an antenna, a receiver, acommutator arranged to put the antenna and receiver into and out ofoperative relation with a frequency fixed with respect to that of thetrains of waves to be received, and means to regulate the time of makeand break of the connections of the receiver to the antenna.

6. Wireless telegraphy receiving apparatus including a commutator forperiod-ical closing, and indicating means so arranged that theindicating means is influenced solely at the exact moment of the passageof receiving waves, synchronizing means, and means to ensure concordanceof phase between the regular succession of continuous waves and theregular succession of closing by the commutator.

7. In wireless telegraphy, an antenna connected to earth, a receiver anda commu tator in the antenna circuit arranged to connect and disconnectthe receiver from the antenna circuit wit-h a frequency equal to that ofthe trains of waves, and means to vary the time of operation of thecommutator.

In testimony whereof I aflix my signature.

ROBERT BENEDICT GOLDSCHMIDT.

Witnesses r CLEMENT S. EDWARDS,

P. BEZI.

